Iron-Peak Element Abundances in Warm Very Metal-Poor Stars

Abstract

We have derived new detailed abundances of Mg, Ca, and the Fe-group elements Sc through Zn (Z = 21-30) for 37 main sequence turnoff very metal-poor stars ([Fe/H] <= -2.1). We analyzed Keck HIRES optical and near-UV high signal-to-noise spectra originally gathered for a beryllium abundance survey. Using typically about 400 Fe-group lines with accurate laboratory transition probabilities for each star, we have determined accurate LTE metallicities and abundance ratios for neutral and ionized species of the 10 Fe-group elements as well as alpha elements Mg and Ca. We find good neutral/ion abundance agreement for the 6 elements that have detectable transitions of both species in our stars in the 3100-5800 Angstrom range. Earlier reports of correlated Sc-Ti-V relative overabundances are confirmed, and appear to slowly increase with decreasing metallicity. To this element trio we add Zn; it also appears to be increasingly overabundant in the lowest metallicity regimes. Co appears to mimic the behavior of Zn, but issues surrounding its abundance reliability cloud its interpretation.

ApJ, in press

References in corpus (16)

• The Gaia mission
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• NLTE abundances of Mn in a sample of metal-poor stars
• New Rare Earth Element Abundance Distributions for the Sun and Five r-Process-Rich Very Metal-Poor Stars
• Improved Laboratory Transition Probabilities for Neutral Chromium and Re-determination of the Chromium Abundance for the Sun and Three Stars
• Improved Laboratory Transition Probabilities for Ce II, Application to the Cerium Abundances of the Sun and Five r-process Rich, Metal-Poor Stars, and Rare Earth Lab Data
• New Extremely Metal-Poor Stars in the Galactic Halo
• Fe I Oscillator Strengths for the Gaia-ESO Survey
• Fe I Oscillator Strengths for Transitions from High-lying Even-Parity Levels
• Improved V II log($gf$) Values, Hyperfine Structure Constants, and Abundance Determinations in the Photospheres of the Sun and Metal-poor Star HD 84937
• Dynamically Tagged Groups of Very Metal-poor Halo Stars from the HK and Hamburg/ESO Surveys
• PUSHing core-collapse supernovae to explosions in spherical symmetry IV: Explodability, remnant properties and nucleosynthesis yields of low metallicity stars
• Fe I oscillator strengths for transitions from high-lying odd-parity levels
• Detailed Iron-Peak Element Abundances in Three Very Metal-Poor Stars
• A new set of chisels for Galactic archaeology: Sc, V and Zn as taggers of accreted globular clusters

Cited by in corpus (2)

• The R-Process Alliance: Fifth Data Release from the Search for R-Process-Enhanced Metal-poor Stars in the Galactic Halo with the GTC
• Revisiting inelastic Cu+H collisions and the non-LTE Galactic evolution of copper